Process control or industrial automation systems can be used to protect, control and monitor industrial processes in industrial plants, for example, manufacturing goods, transforming substances, or generating power, as well as to monitor and control distributed primary systems like electric power, water or gas supply systems or telecommunication systems, including their respective substations. An industrial automation system can have a large number of process controllers distributed in an industrial plant or over a distributed primary system, and communicatively interconnected via a communication system.
Substations in high and medium-voltage power networks can include primary devices such as electrical cables, lines, bus bars, switches, power transformers and instrument transformers, which can be arranged in switch yards and/or bays. These primary devices can be operated in an automated way via a Substation Automation (SA) system. The SA system can include secondary devices, so-called Intelligent Electronic Devices (IEDs), responsible for protection, control and monitoring of the primary devices. The IEDs may be assigned to hierarchical levels, for example, the station level, the bay level, and the process level, the latter being separated from the bay level by a so-called process interface. The station level of the SA system can include an Operator Work Station (OWS) with a Human-Machine Interface (HMI) and a gateway to a Network Control Centre (NCC). IEDs on the bay level, also termed bay units, in turn can be connected to each other as well as to the IEDs on the station level via an inter-bay or station bus primarily serving the purpose of exchanging commands and status information.
IEDs on the process-level can include electronic sensors for voltage (VT), current (CT) and gas density measurements, contact probes for sensing switch and transformer tap changer positions, and/or intelligent actuators (I/O) for controlling switchgears like circuit breakers or disconnectors. Exemplary process-level IEDs, for example, non-conventional current or voltage transformers can include an Analogue to Digital (AD) converter for sampling of analogue signals. Process-level IEDs can be connected to the bay units via a process bus, which can be considered as the process interface replacing the conventional hard-wired process interface. The latter can connect conventional current or voltage transformer in the switchyard to the bay level equipment via dedicated copper wires, in which case the analogue signals of the instrument transformers can be sampled by the bay units.
A communication standard for communication between the secondary devices of a substation has been introduced by the International Electrotechnical Committee (IEC) as part of the standard IEC 61850 entitled “communication networks and systems in substations”. For non-time critical messages, IEC 61850-8-1 specifies the Manufacturing Message Specification (MMS, ISO/IEC 9506) protocol based on a reduced Open Systems Interconnection (OSI) protocol stack with the Transmission Control Protocol (TCP) and Internet Protocol (IP) in the transport and network layer, respectively, and Ethernet as physical media. For time-critical event-based messages, IEC 61850-8-1 specifies the Generic Object Oriented Substation Events (GOOSE) directly on the Ethernet link layer of the communication stack. For fast periodically changing signals at the process level such as measured analogue voltages or currents IEC 61850-9-2 specifies the Sampled Value (SV) service, which like GOOSE builds directly on the Ethernet link layer. Hence, the standard can define a format to publish, as multicast messages on an industrial Ethernet, event-based messages and digitized measurement data from current or voltage sensors on the process level. SV and GOOSE messages are transmitted over a process bus, which may, for example, in cost-effective medium or low voltage substations, extend to neighboring bays, for example, beyond the bay to which the sensor is assigned. In the latter case, the process bus transmits, in addition to the process data, command and/or status related messages otherwise exchanged via a dedicated station bus.
SA systems based on IEC 61850 can be configured and described by means of a standardized configuration representation or formal system description called Substation Configuration Description (SCD). An SCD file includes the logical data flow between the IEDs on the basis of message types or data sets, for example, for every message source, a list of destination or receiver IEDs, the message size in terms of data set definitions, as well as the message sending rates for all periodic traffic like GOOSE, SV and Integrity reports. The SCD file likewise can include the relation between the IEDs as well as the functionality, which the IEDs execute on behalf of the substation, process or switch yard.
EP 2362577 discloses a method for analyzing a communication configuration in a process control system, wherein every network message type or data set configured for transmission from a sender to a receiver IED across an Ethernet switch-based communication network of a PC or SA system is evaluated, and a graphical representation respective of process related operational aspects of each IED involved is generated and displayed. From a logical data flow description that is part of a formal configuration representation of the PC or SA system, sender and receiver IEDs can be retrieved or determined. A single one out of a plurality of operational aspects of the process can be retrieved for each IED from the formal configuration description. Generating the graphical representation of the system includes forming groups of IEDs with identical operational aspects. Thus, the method taught by EP 2362577 can represent the IEDs involved in the network data exchange with respect to operational aspects of the process control system, and depicts message types or data sets statically configured to be transmitted between two IEDs in a manner independent of the number of actual transmits in an operating system. The consequences of IED failures or engineering errors may be recognized, and diagnosing of communication problems at a system design or engineering stage facilitated.
EP 2109204 discloses a method for analysis of a Substation Automation system, which can include an Intelligent Electronic Device and a communication network. An analyzer can be connected to the communication network and can capture messages transmitted by the IED, the messages including a first and a second value (Y1, Y2, Y3) of a particular process quantity (Y), respectively. The captured values can be displayed in a time resolved graphical manner on a screen, and, in case the first and the second value (Y1, Y2, Y3) differ, a discontinuity indicator (Z) graphically marking a change in the value of the process quantity (Y) can likewise be depicted.
EP 2157731 discloses an analysis of a communication configuration in a Process Control (PC) or Substation Automation (SA) system, by evaluating, in a manner irrespective of operational aspects related to the operation of the controlled process or automated substation, every network message, and/or respective message source, configured for transmission across a communication network of the system. From a logical data flow description that is part of a standardized configuration representation of the PC or SA system and which includes, in the form of control blocks, formal information for every message, receiver IEDs are retrieved or determined. For each retrieved receiver IED, the totality of all network messages destined for or directed to this particular receiver IED can be evaluated or processed, for example, in view of a subsequent network load analysis, Virtual Local Area Network assignment, or graphical display of the data flow. Exemplary network messages of interest can include cyclic point-to-point reports, as well as, in terms of IEC 61850, periodic or repeated real-time multicast messages (Sampled Values SV) and event-based multicast messages (Generic Object Oriented Substation Events GOOSE).